All-optical switching (AOS) of magnetization by femtosecond laser pulses has received enormous interest recently. Triggered by the notion that AOS might be realized in ultrathin magnetic systems fulfilling very similar requirements as needed for spintronic control of magnetization in magnetic nanowire racetrack architectures, we envision the development of integrated magneto-photonic memories. In such devices data should be coupled between photonic and magnetic degree of freedom without any intermediate electronic steps, while data should be moved along the magnetic racetrack by means of spin-orbit torques.
In this presentation, we will report on highly efficient AOS and efficient current-induced domain wall motion in the very same system: Pt/Co/Gd trilayers with perpendicular magnetic anisotropy, a reduced magnetic moment by the anti-parallel coupling of Co and Gd sub-layers and displaying strong spin-orbit torques and Dzyaloshinskii-Moriya interaction. It will be shown how the magnetization of such synthetic ferromagnetic thin films systems can be reversed fully deterministically using single fs pulses. Exposing the system to an even number of pulses results in the original magnetization, while an odd number of pulses leads to the reversed magnetic state in a reducible way and even after thousands of laser pulses. Threshold fluences are determined as a function of Co thickness and record low efficiencies corresponding to below 50 fJ needed to switch a 50x50 nm2 are found. Moreover we quantitatively determined spin orbit torques and analyzed the coherent current-driven motion of opposite (up-down and down-up) domain walls.
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